The present invention relates to assembly methods and apparatus and pertains particularly to an apparatus for supporting and bonding lead frames to ceramic bases in a furnace operation.
Lead frames are generally bonded to base members for IC circuits and the like by means of solder glass. The glass is typically melted to its melting point in a furnace and the leads are then attached to the base member by being placed in contact with the solder upon emergence of the base members from the furnace. Frame attachment machines have been developed for this purpose. The major drawback of such machines, however, is that there is a certain degree of rejects requiring rework of certain frame attachment assemblies and rejection of others. Many of these rejects result from the incomplete or inadequate bonding of the solder glass to the lead frames themselves.
The prior art results as shown in FIG. 1 illustrate the typical bonding achieved by the prior art approach. This bonding, as seen, results in the glass tending to rise up between the leads with very little contact of the glass on the side of the leads, and frequently resulting in the glass interfering or obstructing the application wire bond leads to the lead frame.
It is desirable that a method and apparatus by available for improving the bonding of lead frames to ceramic bases.